The Beauharnois Canal is a Canadian canal located in southwestern Quebec. The canal is part of the St. Lawrence Seaway.
Located in Beauharnois-Salaberry Regional County Municipality within the cities of Salaberry-de-Valleyfield, Beauharnois, Saint-Louis-de-Gonzague, and Saint-Stanislas-de-Kostka, the canal connects Lake Saint-Francis to the west (upstream) with Lake Saint-Louis to the northeast (downstream), bypassing a series of rapids on the St. Lawrence River.
The original Beauharnois Canal measured 15 nmi (24 km) in length and was built on the south side of the St. Lawrence River, opening in 1843.
The canal became obsolete and was superseded by the Soulanges Canal in 1899 which ran on the north side of the St. Lawrence River.
The present Beauharnois Canal was built between 1929-1932 on the south side of the St. Lawrence River, measuring 24.5 km in length. This canal was built as part of a hydroelectric development at Beauharnois which saw a dam and power house built to take advantage of the 24 m (83 ft) drop between Lake St. Francis and Lake St. Louis. Some of the electricity is used to power a large aluminum smelter.
In the 1950s, the Beauharnois Canal had 2 locks added as part of the St. Lawrence Seaway project. This in turn superseded the Soulanges Canal. Coordinates: 45°16′19.1″N 73°56′42.7″W / 45.271972°N 73.945194°W